02_Energy_s11b

02_Energy_s11b - Physics 105 Physics Lecture 2 Energy...

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Unformatted text preview: Physics 105 Physics Lecture 2 Energy Spring 2011 Clickers are Required clickers.umd.edu clickers.umd.edu Page 2 Physics 105 – Spring 2011 Physics Clickers - required Setting up your clickers: Set channel 41: Press Go/Ch for 3 sec Yellow/Red flashing light… Press 41 Press Go again Register your clicker at http://clickers.umd.edu/ Id # contains 0 not o(h) Buy at Online or at book store - cheaper version OK; used OK Page 3 Physics 105 – Spring 2011 Physics XR Clickers •Press menu until you see main screen •Use down arrow to select Change Channel •Press Enter •If the current channel is 41, press Enter, otherwise.. •Use keypad to enter 41, then press Enter Register your clicker at http://clickers.umd.edu/ Id # contains 0 not o(h) Physics 105 – Spring 2011 Physics Other Devices You can respond on a laptop, iPhone You Blackberry but you need a license - $16/year See Clickers.umd.edu for details See Page 5 Physics 105 – Spring 2011 Physics Clicker Question Do you believe that the earth is Do getting warmer “mostly because of human activity, such as burning fossil fuels”? 1. yes 2. no 3. unsure Page 6 Physics 105 – Spring 2011 Physics Energy and Power Energy: the capacity to do work Work = force X distance Power: energy per time Physics 105 – Spring 2011 Physics Energy Units Joule = 1 kg m2/s2- Metric unit of energy Joule kWh = 1000 Joule/s for one hour = 3,600,000 J = 3.6 MJ kWh Calorie (food) = 1 kcal = 1,000 calories = 4186 J 1 kcal (Calorie) is the equivalent energy to a 100w light bulb kcal on for about 7 minutes BTU (British Thermal Unit) = energy to raise temperature of 1 BTU lb of water by one degree F= 1,055 J = 0.25 Kcal Quad (Quadrillion (1015) BTU) = 1018J Quad Page 8 Physics 105 – Spring 2011 Physics Energy Equivalents mechanical chemical = 550 Calories 1 gallon of gasoline contains 130 MJ of energy = ~40 Big Macs Page 9 2.3 MJ 1500 kg at 50 m/s (120 mph) Physics 105 – Spring 2011 Physics Power Power = Energy per unit time Power 1 Watt = 1 Joule/s Watt 1 Horsepower = 746 Watts Horsepower - 200 HP engine = 150 kW engine Page 10 Physics 105 – Spring 2011 Physics Question Do we pay for power or energy from the electric Do company? 1 Energy Energy 2 Power Power Page 11 Physics 105 – Spring 2011 Physics My hike up Mt. Fuji The trip started on: Oct 4, 2010 The Trip time up:4.5 Hrs Trip distance up: 9 mi Trip Elevation gain: 1200 m Elevation Energy estimate: E (ideal) = mgh Energy E = 85kg x 10m/s2 x 1200m = 1 MJ E (nonideal) = 5E = 5 MJ Total Energy used in kcal Total - 1 MJ / 4186J/kcal = 1220 kcal - 0.9 kWhr Average Power = Energy/time Average - 3.2x106J/(60x90)s = 300W - This is my power used - Efficiency estimate about 20% - My power output ~300W Page 12 Physics 105 – Spring 2011 Physics Energy needs per adult (kcal/person/day) Primitive – 2,000 Primitive Hunter-gatherer – 5,000 Hunter Early agriculture – 12,000 Early Later agriculture – 20,000 Later Early industrial – 60,000 Early Modern industrial – 125,000 Modern Current U.S. – 250,000 Current Kill something and eat it Kill something, cook it and eat it Use a horse or ox to plow field Use a windmill or waterwheel Steam, coal, wood - make steel Electricity, oil, coal, nat. gas Page 13 Physics 105 – Spring 2011 Physics Do Americans use more energy because 1. 2. 3. 4. We have a higher standard of living We have a bigger country We have cheap energy Our societal norms were established when energy was plentiful 5. Because we can Page 14 Physics 105 – Spring 2011 Physics Energy Page 15 Physics 105 – Spring 2011 Physics How much is a Quad? - 1% of US consumption/yr 472,000 Barrels of Oil/Day for 365 Days or 172,280,000 Barrels of Oil 75 Supertankers → 500,000 Railroad Cars of Coal Annual Production of 20 Three Mile Island Nuclear Plants Page 16 Physics 105 – Spring 2011 Physics U.S. Energy Consumption bySource Total 98 Quads Total Page 17 Physics 105 – Spring 2011 Physics 1850s Fuel Usage Primarily Wood Used Primarily Page 18 Physics 105 – Spring 2011 Physics 1900s Fuel Usage Wood and Coal Use about equal Wood Easy transition to make because Easy both are solid fuel Oil = liquid need to change furnace Oil technology Page 19 Physics 105 – Spring 2011 Physics 1950s Fuel Usage Big switch to fossil fuels is Big complete More use of liquid and gaseous More fuels Very little use of renewable fuels or Very nuclear Page 20 Physics 105 – Spring 2011 Physics 1990s Fuel Usage Oil is now the dominant fuel type Oil followed by natural gas and coal. More use of alternative fuels and More nuclear Wood primarily used in third world Wood nations Page 21 Physics 105 – Spring 2011 Physics What is this energy being used for? liquid fuel electric 34% 35% heat <100 heat 100-600 heat >600 Liquid Fuel is for vehicle Liquid use Heating less than 100 oC Heating is space-heating Other heating is for Other industrial purposes Nuclear Electricity Nuclear generation is only 8% of total power Page 22 Physics 105 – Spring 2011 Physics What is this energy being used for? Physics 105 – Spring 2011 Physics U.S. Energy Use In 1991, the U.S. consumed 81.5 quads In Today we are using a little under100 quads Today How much is a quad? How - 1 quad = 1015 (1,000,000,000,000,000) BTUs - 1 BTU = energy required to warm 1 lb water 1 oF - 1 quad = 1.05 x 1018 J -> 100 quads = ~ 1020 J Page 24 Physics 105 – Spring 2011 Physics Average Power Per Person in the US 100 quads of energy in a year - how much average power? 100 - ~πx 107 seconds/year = 3.15 x 107 seconds/year - 1020 J/year / 3.15x107 seconds/year = 3x1012W (3TW) - 3 trillion watts is the average power consumed in the US - 300 Million people - 3x1012W/3x108 people = 104W/person = 10kW/person - 24 hrs per day (includes industry, travel, heating/AC everything - 10kW * 86,400 sec/day = 864,000 J/d = 206,000kcal/d - (remember we saw 250,000 kcal/per day/adult before) Page 25 Physics 105 – Spring 2011 Physics Energy Consumption per Person 327 MBTU/yr = 896,000 BTU/day = 224,000 Kcal Page 26 Physics 105 – Spring 2011 Physics Physics 105 – Spring 2011 Physics U.S. Energy Flow, 2004 (Quads) 30% of U.S. primary energy is imported Page 28 Physics 105 – Spring 2011 Physics What Percentage of US Energy comes from Renewable Sources 1. 3% 2. 8% 3. 15% 4. 20% 5. 25% 6. 50% Page 29 Physics 105 – Spring 2011 Physics U.S. Energy Flow, 2009 (Quads) 82% of primary energy is from fossil fuels, with 57% of the petroleum imported Page 30 Physics 105 – Spring 2011 Physics ...
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This note was uploaded on 02/28/2011 for the course PHYS 105 taught by Professor Staff during the Spring '08 term at Maryland.

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